High-pressure cleaning apparatus

ABSTRACT

In a high-pressure cleaning apparatus comprising an electric motor arranged in a housing, a high-pressure pump arranged in a housing with at least one piston entering a pump chamber in a sealed manner, and a swash plate carried by a motor shaft protruding from the housing of the electric motor, with the piston or pistons of the high-pressure pump resting in a resilient manner against the swash plate, in order to achieve electrical insulation in the region of the swash plate drive, it is proposed that the transition from the motor shaft via the swash plate to the piston or pistons be electrically interrupted by an electrically insulating material being interposed therebetween.

This application is a continuation of PCT/EP94/03086 filed sep. 15,1994.

BACKGROUND OF THE INVENTION

The invention relates to a high-pressure cleaning apparatus comprisingan electric motor arranged in a housing, a high-pressure pump arrangedin a housing, at least one piston entering a pump chamber in a sealedmanner, and a swash plate carried by the motor shaft of the electricmotor, with the piston or pistons of the high-pressure pump resting in aresilient manner against the swash plate, the transition from the motorshaft via the swash plate to the piston or pistons being electricallyinterrupted by an electrically insulating material interposedtherebetween.

For safety reasons, it is necessary to electrically insulate the pumpand the pump housing relative to the electric motor and the housing ofthe electric motor. In a known high-pressure cleaning apparatus in whichthe pistons of the high-pressure pump are driven by an eccentric drive,this is accomplished, inter alia, by the motor shaft of the electricmotor carrying an eccentric being provided with a plastic covering (DE88 01 028-U1). However, there is no hint to be found in this publicationas to how this object could be accomplished specifically in ahigh-pressure cleaning apparatus with a swash plate drive.

It is also known, in such an axial piston pump, to design the swashplate as a molded part made of plastic material so that an electricalinsulation is thereby achievable in the strand consisting of motorshaft/swash plate/piston (DE-U 9 320 361).

The object of the invention is to so design a generic high-pressurecleaning apparatus, i.e., a high-pressure cleaning apparatus with aswash plate drive, that a more complete electrical separation of thepump part and the motor part is possible.

SUMMARY OF THE INVENTION

This object is accomplished in accordance with the invention in ahigh-pressure cleaning apparatus of the kind described at the beginningby the housing of the electric motor consisting of a pot-shaped housingpart and a component constituting part of the housing of thehigh-pressure pump, and by an intermediate layer of electricallyinsulating plastic material being arranged between the stator of theelectric motor and the component of the housing.

Accordingly, with such a two-part division of the encapsulation of themotor, the electric motor is enclosed on all sides by a housing part andby the housing of the high-pressure pump, with the housing of thehigh-pressure pump closing the housing part on one side, for example, inthe form of a cover or hood. Optimum electrical separation of the motoris now achieved by an electrically insulating intermediate layer beinginserted between the stator of the electric motor, on the one hand, andthis part of the pump housing which closes off the electric motor. It isthus possible to also use metallic and hence electrically conductivehousings for the high-pressure pump which, nevertheless, are thenelectrically completely separated from the electric motor.

In accordance with a preferred embodiment, provision may, furthermore,be made for an intermediate layer of electrically insulating plasticmaterial to be arranged between the stator of the electric motor and thepot-shaped housing part of the electric motor. Thus, a correspondingelectrically insulating intermediate layer may be provided in this areaof the second part of the electric motor encapsulation, too, and so thispart of the encapsulation may also be made of electrically conductivematerial.

It is advantageous for the intermediate layer to be in the form of foil.

In particular, provision may be made for the motor shaft to consist ofan electrically insulating plastic material.

In a modified embodiment, provision is made for the motor shaft to becovered with a layer of electrically insulating plastic material atleast in the region in which the swash plate rests thereagainst.

In another embodiment, the motor shaft carries a cap consisting ofelectrically insulating plastic material in the region in which theswash plate rests thereagainst.

In a particularly preferred embodiment, provision is made for the swashplate to be held at the end face thereof by a screw on the motor shaftwhich rests with a head consisting of electrically insulating plasticmaterial against the swash plate. It is thereby ensured that, on the onehand, the high strength properties of a metallic screw can be exploited,but, on the other hand, the screw does not establish electrical contactbetween the swash plate, on the one hand, and the motor shaft, on theother hand.

In a preferred embodiment, the screw may consist of metal and its headmay be surrounded by an electrically insulating covering. It isexpedient for the covering to carry on the outside thereof applicationsurfaces for a wrench. A screw provided in this way with a plasticcovering can then also be screwed-in in the usual way.

It is, furthermore, advantageous for a metallic force-transmittingelement embedded in the plastic covering to be arranged on the screw.This can be, for example, a washer with a larger outer diameter than thehead of the screw.

It is also advantageous for the covering to be injection molded onto thehead of the screw, i.e., for the head and possibly also theforce-transmitting element to be jointly embedded by injection molding.

In a further preferred embodiment, the swash plate consists of anelectrically insulating plastic material.

Provision may also be made for the swash plate to receive an abutmentdisc against which the piston or pistons rest, and for the abutment discto consist of electrically insulating plastic material. In theseembodiments, metallic connections may be used between the swash plateand the motor shaft, and the motor shaft itself may also be of metallicdesign.

A further possibility of electrical separation is obtained by thepistons consisting of electrically insulating plastic material or beingsheathed by an electrically insulating plastic material.

The measures explained above may, of course, also be used incombination.

Furthermore, provision may be made for an intermediate layer ofelectrically insulating plastic material to be arranged between thehousing of the pump and the housing part of the electric motor.

This intermediate layer is preferably in the form of a ring.

This ring may carry projections which lie between the projections of thehousing of the pump and the housing part of the electric motor. Theseprojections are thereby also electrically insulated from one another.

Provision is made for the projections to be connected to each other by ascrew which consists of metal and is surrounded by a jacket ofelectrically insulating plastic material in such a way that the metallicpart of the screw is electrically separated at least from one of theprojections. It is expedient for the jacket to be an insert sleeve intowhich the screw is inserted.

In this way, perfect electrical separation is also achieved between thehousings of the electric motor and the pump even when these parts areconnected to each other by metallic screws.

In a further preferred embodiment, the housing of the pump may beprovided with a covering of electrically insulating plastic material oritself consist of electrically insulating plastic material.

Furthermore, it is advantageous for a chamber for receiving electricalleads and/or switching elements to adjoin the housing of the pump and tobe electrically separated from the housing of the pump by anelectrically insulating plastic material interposed therebetween. Inthis way, complete electrical insulation from the pump and the pumphousing is also achieved in the area of the electrical supply lines andso a high-pressure cleaning apparatus constructed in accordance with theabove description meets increased safety requirements.

The following description of preferred embodiments of the inventionserves in conjunction with the drawings to explain the invention infurther detail.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a side view of a high-pressure cleaning apparatus in a partlybroken open illustration, with a motor pump unit shown in section in thelongitudinal direction;

FIG. 2 a longitudinal sectional view through the swash plate drive ofthe motor pump unit of FIG. 1; and

FIG. 3 an enlarged longitudinal sectional view in the area in which thehousings of the electric motor and the pump are connected.

DETAILED DESCRIPTION OF THE INVENTION

A motor pump unit 2 comprising an electric motor 3 and a high-pressurepump 4 is arranged in a housing 1 of a high-pressure cleaning apparatus.The electric motor 3 is positioned in a pot-shaped housing 5 having atthe bottom 6 a central rotary bearing means 7 for a motor shaft 8 whichis part of a rotor 9. The rotor 9 is surrounded by a stator 10 with astator winding 11. Inserted between the stator 10 and the housing 5 ofthe electric motor is a foil 12 made of an electrically insulatingplastic material so the stator is completely insulated relative to thehousing 5 of the electric motor.

The end of the motor shaft 8 opposite the bearing means 7 and also oneof the two stator windings 11 protrude from the housing 5 of theelectric motor 3 and are covered in this area by a hood 13 which is partof a housing 14 of the high-pressure pump 4. The hood 13 receives arotary bearing means 15 for the motor shaft 8 so the motor shaft 8 ismounted between the bearing means 7 and 15. It extends through thebottom of the hood 13 and protrudes into a swash plate chamber 16 in theinterior of the housing 14. The motor shaft 8 is connected there to aswash plate 17 which serves as drive means for the high-pressure pump 4.

This high-pressure pump 4 comprises several pump chambers 18, only oneof which is illustrated in FIG. 1. This pump chamber 18 communicates viaan inlet valve 19 with a suction line 20 and via an outlet valve 21 witha pressure line 22. A cylindrical piston 23 which is mounted fordisplacement in a guide means 24 protrudes into the pump chamber 18. Thepiston 23 is pressed against a ring-shaped abutment disc 27 by a helicalspring 25 which concentrically surrounds the guide means and the pistonand is supported, on the one hand, at the pump chamber 18 and, on theother hand, at a supporting collar 26 of the piston 23. The abutmentdisc 27 is mounted for rotation in the swash plate via a ball bearing 28so that upon rotation of the motor shaft and thus of the swash plate,the pistons pressed against the abutment disc 27 are oscillatinglydisplaced in the guide means.

In the area of the rotary bearing means 15, the motor shaft 8 carries acap 29 made of electrically insulating plastic material which extendsover its end. The cap 29 engages in the inner ring 30 of a ball bearing31 which forms the rotary bearing means 15. This prevents an electricalconnection between the motor shaft 8, on the one hand, and the rotarybearing means 15, on the other hand, and thus also an electricalconnection between the motor shaft 8, on the one hand, and the housing14 of the high-pressure pump, on the other hand.

With a central recess 32, the swash plate 17 embraces the front end ofthe cap 29 and positions itself against a step 33 of this cap 29. Therecess 32 and the front end of the cap 29 can be of non-circularconfiguration so that swash plate and motor shaft are therebyrotationally fixedly connected to each other.

In this position, the swash plate is held by a tightening screw 34 onthe motor shaft 8. This tightening screw 34 is screwed at the end facethereof into a threaded bore 35 of the motor shaft 8. The tighteningscrew 34 consists of metal and carries between its head 36 and thethreaded area 37 a supporting disc 38, the outer diameter of which islarger than that of the head 36. The head 36 and the supporting disc 38are jointly surrounded by an electrically insulating plastic materialwhich has the shape of a larger head 39 and embeds the upper part of thetightening screw 34 within it. With its underside 40, this head 39 liesagainst the swash plate 17 and presses it axially against the motorshaft 8. The swash plate 17 is thereby fixed on the motor shaft. Theunderside 40 has a central recess 41 in which the cap 29 engages withthe front part thereof. This results in a continuous jacket ofelectrically insulating plastic material in the area of the end of themotor shaft 8 and the tightening screw 34. In this area, no metal partsare accessible from the outside. In this way, the swash plate and thehousing of the motor are electrically fully insulated from the motorshaft.

The head 39 may carry on the sides thereof application surfaces 42 for awrench, for example, the head may have a hexagonal cross section.

The free rim 43 of the hood 13 adjoins the rim of the housing 5 of theelectric motor via an interposed ring 44 made of electrically insulatingplastic material. This ring 44 thus insulates the housing 5 of theelectric motor from the hood 13 and hence from the housing 14 of thepump.

In order to connect the hood, on the one hand, and the housing of theelectric motor, on the other hand, to each other, both parts carry sideprojections 45, 46 (FIG. 3), one of which has a through-bore 47 and theother an internally threaded bore 48. The ring 44 also has in the areaof the projections 45 and 46 side projections 49 which are arrangedbetween the projections 45 and 46 and separate these electrically fromeach other. Also arranged in the area of the projection 49 is athrough-bore 50 which is in alignment with the through-bore 47 and theinternally threaded bore 48.

A tightening screw 51 is inserted into the through-bores 47 and 50 andscrewed into the internally threaded bore 48. A sleeve 52 made ofelectrically insulating plastic material is positioned on the upper partof this tightening screw 51. The sleeve 52 surrounding the tighteningscrew 51 protrudes into the through-bore 47 of the one projection 45 andthereby electrically separates the tightening screw 51, which consistsof metal, from the projection 45. This construction ensures that thereis also no electrically conductive connection through the projectionsand the tightening screws in the connecting area of the housing 5 andthe housing 14, although the housings and the screw can consist ofelectrically conductive material, in particular, of metal.

The electrical separation of the electric motor and the pump can befurther improved by the stator winding 11 facing the high-pressure pump4 also being covered relative to the hood 13 and thus relative to thehousing 14 with a foil 53 consisting of electrically non-conductive^(*)plastic material. As illustrated in FIG. 1, this can be laid so as toextend along the hood, but it is also possible to cover the statorwinding 11 with an appropriate foil.

Adjoining the housing 14 of the pump is a chamber 54 which receiveselectrical leads 55 or switching elements. This chamber either consistsitself of electrically insulating plastic material or it is fixed in anelectrically separated manner on the housing 14 of the pump withelectrically insulating plastic material interposed therebetween so thatthe lines 55 and electrical switching elements in the interior of thechamber 54 are electrically insulated by the chamber itself relative tothe housing 14 of the pump.

In particular, polyamides, polyesters, polyurethanes or variousthermosetting plastics can be used as electrically insulating plasticmaterial.

What is claimed is:
 1. A high-pressure cleaning apparatus, comprising:anelectric motor with a stator arranged in a motor housing for driving amotor shaft; said motor housing comprising a first portion which extendscircumferentially about said stator; a high-pressure pump which isadapted to be driven by said motor shaft and which has at least onepiston and pump chamber arranged in a pump housing; said pump housingcomprising a second portion which extends circumferentially about saidat least one piston and pump chamber; a metallic hood component whichforms a common end portion of said motor housing and said pump housing;said hood component receiving a rotary bearing means for supporting saidmotor shaft; said hood component extending substantially from saidrotary bearing means toward said first portion of said motor housing forclosing an end of said motor housing, and toward said second portion ofsaid pump housing for closing an end of said pump housing; anelectrically insulating material interposed between said motor shaft andsaid at least one piston and pump chamber; and an intermediate layer ofelectrically insulating material that extends, at least in part, alongsaid hood component on a side of said hood component that faces saidstator; wherein: said electrically insulating material and saidintermediate layer of electrically insulating material serve toelectrically separate said high pressure pump and said electric motor.2. A high-pressure cleaning apparatus as defined in claim 1,wherein:said hood component is unitary with said second portion of saidpump housing.
 3. A high-pressure cleaning apparatus as defined in claim1, wherein:said hood component has a free rim that is adapted to besecured to said first portion of said motor housing for closing said endof said motor housing.
 4. A high-pressure cleaning apparatus as definedin claim 3, further comprising:an insulative ring interposed betweensaid free rim and said first portion of said motor housing.
 5. Ahigh-pressure cleaning apparatus as defined in claim 1, wherein:saidfirst portion comprises a pot-shaped housing part which extendscircumferentially about said stator; and an intermediate layer ofelectrically insulating plastic material is arranged between said statorand said pot-shaped housing part.
 6. A high-pressure cleaning apparatusas defined in claim 1, wherein:said intermediate layer is in the form offoil.
 7. A high-pressure cleaning apparatus as defined in claim 1,wherein:said first portion comprises a pot-shaped housing part whichextends circumferentially about said stator; and an intermediate layerof electrically insulating plastic material is arranged between saidpump housing and said housing part.
 8. A high-pressure cleaningapparatus as defined in claim 7, wherein:said intermediate layer ofelectrically insulating plastic material is in the form of a ring.
 9. Ahigh-pressure cleaning apparatus as defined in claim 8, wherein:saidring carries projections which lie between projections of said pumphousing and said housing part, respectively.
 10. A high-pressurecleaning apparatus as defined in claim 9, wherein:said projections areconnected to each other by a screw which comprises metal and issurrounded by a jacket of electrically insulating plastic material insuch a way that the metallic part of said screw is electricallyseparated at least from one of said projections.
 11. A high-pressurecleaning apparatus as defined in claim 10, wherein:said jacket is aninsert sleeve into which said screw is inserted.
 12. A high-pressurecleaning apparatus as defined in claim 1, wherein:said motor shaftcomprises electrically insulating plastic material.
 13. A high-pressurecleaning apparatus as defined in claim 1, wherein:said high-pressurepump comprises a swash plate, with said at least one piston resting in aresilient manner against said swash plate; and said motor shaft iscovered with a layer of electrically insulating plastic material atleast in a region against which said swash plate rests.
 14. Ahigh-pressure cleaning apparatus as defined in claim 1, wherein:saidhigh-pressure pump comprises a swash plate, with said at least onepiston resting in a resilient manner against said swash plate; and saidmotor shaft carries a cap made of electrically insulating plasticmaterial in a region against which said swash plate rests.
 15. Ahigh-pressure cleaning apparatus as defined in claim 1, wherein:saidhigh-pressure pump comprises a swash plate, with said at least onepiston resting in a resilient manner against said swash plate; saidswash plate is held at an end face thereof by a screw on said motorshaft; and said screw has a head comprising electrically insulatingplastic material which rests against said swash plate.
 16. Ahigh-pressure cleaning apparatus as defined in claim 15, wherein:saidscrew comprises metal and its head is surrounded by an electricallyinsulating covering.
 17. A high-pressure cleaning apparatus as definedin claim 16, wherein:an exterior of said covering carries applicationsurfaces for a wrench.
 18. A high-pressure cleaning apparatus as definedin claim 16, wherein:a metallic force-transmitting element embedded insaid covering is arranged on said screw.
 19. A high-pressure cleaningapparatus as defined in claim 18, wherein:said covering is injectionmolded onto said head of said screw.
 20. A high-pressure cleaningapparatus as defined in claim 1, wherein:said high-pressure pumpcomprises a swash plate, with said at least one piston resting in aresilient manner against said swash plate; and said swash platecomprises electrically insulating plastic material.
 21. A high-pressurecleaning apparatus as defined in claim 1, wherein:said high-pressurepump comprises a swash plate; and said swash plate receives an abutmentdisc against which said at least one piston rests; and said abutmentdisc comprises electrically insulating plastic material.
 22. Ahigh-pressure cleaning apparatus as defined in claim 1, wherein:said atleast one piston comprises electrically insulating plastic material oris sheathed with an electrically insulating plastic material.
 23. Ahigh-pressure cleaning apparatus as defined in claim 1, wherein:saidpump housing is provided with a covering of electrically insulatingplastic material.
 24. A high-pressure cleaning apparatus as defined inclaim 1, wherein:said pump housing comprises an electrically insulatingplastic material.
 25. A high-pressure cleaning apparatus as defined inclaim 1, wherein:a chamber for receiving electrical leads and/orswitching elements adjoins said pump housing, said chamber beingelectrically separated from said pump housing by an electricallyinsulating plastic material being interposed therebetween, or saidchamber itself comprising an electrically insulating plastic material.26. A high-pressure cleaning apparatus as defined in claim 5,wherein:said intermediate layer is in the form of foil.
 27. Ahigh-pressure cleaning apparatus as defined in claim 14, wherein:saidswash plate is held at an end face thereof by a screw on said motorshaft which rests with a head comprising electrically insulating plasticmaterial against said swash plate.
 28. A high-pressure cleaningapparatus as defined in claim 1, wherein:said intermediate layer ofelectrically insulating material comprises plastic.